Linux puskom-ProLiant-DL385-Gen10 5.4.0-150-generic #167~18.04.1-Ubuntu SMP Wed May 24 00:51:42 UTC 2023 x86_64

//usr/share/netpbm/palmgray4.map

 P2
# 16 level grayscale palette
4 4
15
 0  1  2  3
 4  5  6  7
 8  9 10 11
12 13 14 15